Grammarly proofread 400+ freelancer profiles from all eight categories of the Elance platform for grammar, spelling, and punctuation errors. To adjust for quality of work, they only selected freelancers with an average rating of four stars or above. Then they looked at correlation between earnings and number of mistakes. They hope the direction of the data spurs some thought and conversation about the importance of good writing. Their goal is to raise awareness for the importance of good writing. Here’s the chart with their findings:

Here’s the link to the Grammarly site in case you’d like to check some of your own writing for errors: It couldn’t hurt!